1. Field of the Invention
The present invention relates generally to a semiconductor technique and more particularly to a method for depositing a flowable material using an alkoxysilane or aminosilane precursor on a substrate having an irregular surface.
2. Description of the Related Art
In recent years, there has been a practice of using a plasma CVD apparatus equipped with a low-temperature susceptor to deposit onto a silicon substrate an insulating liquid material having flowability, after which the deposited material is filled by means of surface tension into trenches of semiconductor circuitry having irregular surface. According to an evaluation of low-temperature plasma CVD using an alkoxide siloxane material having one Si, however, filled shape problems called “voids” occurred in trenches when trenches having irregular surface were completely filled with a material of low flowability (refer to U.S. Patent Laid-open No. 2008/0076266A1 for example). Based on the above, flowability was improved by introducing a hydrocarbon gas expressed by CxHy (refer to the same document mentioned above). As a result, however, use of such hydrocarbon gas as an additive gas resulted in a higher content of carbon in the liquid insulation material that has been formed into a film and consequently large amounts of CxHyOH, Si—CxHy, SiOH, etc., were taken in.
In view of the above, the inventors of the present invention conducted various experiments to evaluate the removal of the aforementioned substances in post-deposition processes, but in all cases the shrinkage of film became extremely high and the film cracked or its density in trenches having irregular surface became low, thereby creating hole-like spherical voids, and these conditions were difficult to improve. In particular, the film shrinkage exceeded 30% in many cases, although it became as low as approx. 20% under certain conditions. As a result, it was considered that flowability and film shrinkage would be in a trade-off relationship.